Statistics show that an alarming number of children drown in private swimming pools every day. Drowning is particularly prevalent among young children who do not know how to swim, or are not capable of getting out of pools under emergency or accidental situations.
A large number of different types of swimming pool alarms have been proposed and even marketed. However, to the best of this applicant's knowledge, none of these devices have had any success due to their unacceptable large number of false alarms. A problem with the wave motion and pressure sensor type devices is the surface condition of the water being affected by wind and pool cleaning equipment. The pulsed echo type devices cannot detect objects obscured by odd shaped walls as most modern shaped pools. Regular hydrophones are simply microphones in a waterproof inclosure and react to a wide range of frequencies such as low flying aircraft, dogs barking, and other sounds external to the water, which make them unacceptable.